Process and apparatus for electroplating annular bodies



April 2, 1968 a KIEFER ET AL PROCESS AND APPARATUS FOR ELECTROPLATINGANNULAR BODIES Filed April 30, 1964 ABSTRACT (BF THE DISCLGSUREElectroplating the internal surface of an annular body, such as abearing, by immersing the bearing in an electrolysis bath, connectingthe outer axially extending surface of the bearing as cathode, andpassing current through the bath from an anode disposed externally ofthe annular body. The annular body is held between nonconducting platesdisposed at the ends of the annular body and each having an openingcoaxial with the annular body.

The subject of the application is an apparatus for the internalelectroplating of annular bodies.

It is in the prior art to create an electrodeposit on the internalsurface of annular bodies, such as bearing half-shells made of steel andaluminum compound or other bearing metals, in internal anodeelectroplating apparatus. Thus, half-shells are assembled in pairs toform a circular ring for this purpose, and they are placed inappropriate mountings in the center of which the anode (such as a roundrod of nickel, copper or lead) is placed. The objects to beelectroplated are connected as the oathode of the apparatus. Like theanode, they draw their current through the suspension arm of theelectroplating apparatus or through a cable connection to the currentsource. It is customary to electroplate one-piece annular bodies, suchas bearing sleeves, with an internal anode in a manner similar to thatdescribed above. In such operations, however, due to the relativelyshort distance between anode and cathode, the accuracy which istherefore required in the geometrical positioning of the anode and ofthe half-shells or annular bodies in relation to one another, is adecided disadvantage. This can be explained briefly by means of anexample: if the anode is a mere one millimeter off center in relation toa bushing with a diameter of about 50 mm., the result can be adifference of as much as 5 microns in the thickness of the galvanicplating, which, in the case of an average overall deposit of microns,amounts to Furthermore, the use of an internal anode results in lossesof time in connection with the loading of the electroplating apparatus,which cannot conveniently be made automatic in the case of annularbodies.

Lastly, it must be mentioned that disturbances in the electrolyticequilibrium are produced during the electroplating process by the factthat the area ratio of the anode rods in the center of the annularbodies to the cathode area has to be exceedingly unfavorable. Due to thedissolution of the anode during the plating process, continual changesin the anode-to-cathode surface-area ratio occur, which results inadditional uncertainty of the electroplating conditions. Also, theremoval of anode metal during the electrolysis results in greater dangerof the decentering of the anode.

It has, for these reasons, already been attempted to replace theinternal anode in electroplating with an external anode in the platingtank. However, the disclosures which have become known in this regarddeal exclusively States Patent 0 with plating equipment for half-shells,not with one-piece annular bodies or bearings as in the case of thisapplication. The invention is therefore aimed at the problem of makingthe use of external anodes possible also in the case of bearing bushes,and half-shells assembled into annular bodies.

According to the invention, an annular body is electroplated bydisposing the annular body coaxially with respect to aligned, equaldiameter openings in non-conducting side plates positioned one at eachend of the body in close-fitting engaging relation therewith. Theannular body and the side plates are immersed in an electrolysis bathoutfitted with an anode and a cathode connection, and electricalconnection is made between the cathode connection and the outer axiallyextending surface of the body, and passing a current through the bath toelectroplate the internal surface. Desirably a rack, speciallyconstructed for use according to the procedure of the invention, is usedfor holding a plurality of annular bodies. The rack can comprise avertically elongated chamber defined by end walls, two sidewalls and abottom, and is open at the top. A plurality of equal diameter openingsat equal vertically spaced intervals are provided in each sidewall, andthe openings in the two sidewalls are in aligned relation so that thereis provided a vertical row of spaced pairs of openings, the openings ineach pair being coaxial and the axes of said pairs being verticallyaligned. One or more vertical rows of opening pairs can be provided.Exposed surfaces of the end walls and sidewalls, below a level above andadjacent the uppermost pair of openings, are non-conducting. Desirably,to facilitate making electrical connection to the outer axiallyextending surface of the annular bodies, the bottom is nonconductingexcept for a portion or portions thereof aligned with the axes of thevertical row or rows of opening pairs. The axis of the lowermost pair ofopenings in each vertical row can be spaced from the exposed surface ofthe bottom corresponding thereto, one half the spacing of the axes ofeach vertical row from each other. Then, in each vertical row of openingpairs, a number of annular bodies equal to the number of opening pairs,and each having an outside diameter equal to the vertical spacing of theopenings and of a size to be received in the chamber, can be placedthereon one atop the other with the bottom body in electrical connectionwith the exposed surface of the bottom and each body in electricalconnection with the body next above. One annular body will then bedisposed coaxially with respect to the axes of each opening pair in therow. Means are provided for making electrical connection to the exposedportion or portions of the bottom with a cell cathode connection, sothat the lowermost annular body or bodies can be connected as cathode,and serve to connect the annular bodies above as cathode. The rack canbe suspended in an electrolyte bath and the electroplating effected bypassage of a current from an anode provided in said bath, through thebath and to the annular body cathodes.

The invention is further described in reference to the accompanyingdrawings, wherein:

FIG. 1 is a side 'elevation view of a rack according to the invention;

FIG. 2 is an end elevation of the rack shown in FIG.

FIG. 3 is a cross-section of the rack shown in FIG. 1, taken along line3-3 in FIG. 1;

FIG. 4 is a cross-section taken on line 44 in FIG. 3; and FIG. 5 is aschematic representation of an electrolysis bath wherein a rackaccording to the invention is used.

In the various views of the drawings, like reference characters refer tocorresponding parts.

Referring to the drawings, the rack l is formed by sidewalls 2 which canbe of plastic, end walls 5, and bottom wall 511. The rack has an opentop 5b, by way of which annular bodies can be placed between thesidewalls. The rack is divided into a plurality of compartments 2 by thepartitions 3 and end pieces 3a, and a row of vertically spaced openings8 is provided for each compartment. As is described in more detailabove, these openings are of equal diameter and are equally spaced, andthe openings in the two sidewalls are arranged to provide opening pairsin which the openings of each pair are coaxial.

As can be best seen in FIG. 3, the sidewalls 5 are made up of the metalstrip 11 and rubber covering 12, and are fixedly secured to the endpieces 3a by bolting 13. The bolting 13 can be suitably covered byinsulating material, or, can be by utilization of a non-conductingmaterial. The construction of the bottom is best seen in FIG, 4. Thebottom is formed of the metal strip 11a and the rubber covering 12a.Portions 15 of the bottom metal strip are uncovered so that electricalconnection can be made at these portions. Desirably, the metal strip 11aof the bottom is integral with the metal strip 11 of the sidewall,whereby electrical connection to the exposed portions 15 of the bottom,and the providing of a rigid frame for the rack is facilitated. Thebottom is also provided with weep holes 16 which facilitate suitabledrainage.

At the upper portion of the rack, the sidewalls 5 connect with across-piece 17 to which a suspending means 9 is connected. The sidewallsare rubber covered to the upper end thereof, and the cross-piece 17 isalso rubber covered, and, further, includes a metallic core (not shown)in electrical connection with the metal strip of the sidewalls. Thesuspending means 9 includes a metallic core in electrical connectionwith the metallic core of the crosspiece 17, and the lower portion 18thereof is rubber covered, while the upper portion 19 thereof isuncovered to expose the metal to facilitate making electricalconnection. Thus, a circuit is provided from the upper portion 19 of thesuspending arm to the exposed portions 15 of the bottom, the circuitbeing through the suspending arm, the cross-piece 17, the sidewalls 5,and the bottom 5a.

The spacing of the axis of each of the lowermost open.- ings 8, from theexposed portion 15 of the bottom 5a, is equal to the outside diameter ofthe annular bodies to be electroplated, and the axis to axis spacing ofthe openings in each vertical row is equal to the outside diameter ofthe annular bodies to be electroplated. Further, the spacing of thesidewalls 2 from each other is such that the annular bodies whendisposed with their axes parallel to the axes of the openings, can bereceived between the sidewalls in close-fitting engaging relationtherewith.

In operation, the compartments 2 are filled with annular bodies, and ineach compartment the lowermost annular body is in electrical connectionwith the exposed portion 15 of the bottom, which corresponds to thecompartment in question, The annular bodies are disposed one atop theother, so that the outer surface of the bodies is in electricalconnection, each annular body being in electrical engagement with theannular body or bodies above and/ or below it. The rack can then besuspended from a holder 18 (FIG. 5), which serves as a cathodeconnection and is connected to a source of negative voltage. The rack,immersed in the electrolyte bath 19 contained in the tank 20, also hasimmersed therein the anodes 21, which are connected to the source ofpositive voltage. Electroplating can then be performed in the usualmanner.

The size of the openings 8 is preferably slightly greater than theinside diameter of the annular bodies. The spacing of thesidewalls 2with respect to the axial length of the annular bodies can be so that aslight positive clearance is provided between the bodies and thesidewalls, to facilitate placement and removal of the annular bodies 4.The sidewalls 2 can be constructed of any suitable nonconducting plasticmaterial. The rack of the invention is particularly well suited for theplating of the internal surface of bushings.

While the invention has been described with respect to particularembodiments thereof, these embodiments are merely representative, and donot serve to define the limits of the invention.

What is claimed is:

1. A rack for holding annular bodies for electroplat ing the innersurface thereof comprising:

(a) a vertically elongated chamber defined by end walls, two sidewalls,and a bottom, and having an open top, a plurality of equal diameteropenings at equal vertically spaced intervals in each of said sidewalls,the openings in the two sidewalls being aligned providing a vertical rowof spaced pairs of openings, the openings in each pair being coaxial andthe axes of said pairs being vertically aligned,

(b) substantially all of the exposed surfaces of said chamber below alevel above and adjacent the uppermost pair of openings beingnon-conducting,

(c) means for suspending said rack in an electroplating bath, and meansfor making electrical connection to the external surface of annularbodies disposed within said chamber,

(d) the axis of the lowermost pair of openings being spaced from thebottom onehalf the spacing of said axes from each other.

whereby a number of annular bodies equal to the number of pairs ofopenings and each having an outside diameter equal to the verticalspacing of said openings and of a size to be received in said chamber,can be placed therein one atop the other with each annular body inelectrical connection with the annular body next below, with one annularbody coaxially disposed with. respect to the axis of each opening pair.

2. A rack for holding annular bodies for electroplating the innersurface thereof comprising:

(a) a vertically elongated chamber defined by end walls, two sidewallsand a bottom, and being open at the top, a plurality of equal diameteropenings at equal vertically spaced intervals in each sidewall, theopenings in the two sidewalls being aligned providing a vertical row ofspaced pairs of openings, the openings in each pair being coaxial andthe axes of said pairs being vertically aligned,

(b) exposed surfaces of the end walls and sidewalls being non-conductingbelow a level above and adjacent the uppermost pair of openings, and aportion of the inner surface of the bottom wall including the portionthereof aligned with the axes of said openings being conducting,

(c) the axis of the lowermost pair of openings being spaced from saidexposed surface of the bottom onehalf the spacing of said axes from eachother,

(d) means for suspending said rack in an electroplating bath,

(e) means for making electrical connection to said exposed surface ofthe bottom,

whereby a number of annular bodies equal to the number of pairs ofopenings and each having an outside diam eter equal to the verticalspacing of said openings and of a size to be received in said chamber,disposed therein one atop the other, with the bottom body in electricalconnection with said exposed surface of the bottom and each body inelectrical connection with the body next above, 7 with one annular bodycoaxially disposed with respect to the axis of each opening pair.

3. A rack according to claim 2, said chamber comprising a plurality ofvertical rows of spaced pairs of openings, as aforesaid, there being aconducting portion of said bottom wall for each vertical row of openingpairs, the conducting portion for each pair being aligned with the axesof its opening pairs.

4. A rack according to claim 2, the sidewalls being of plastic, the endwalls and bottom being formed of metal covered by insulating material,the metal of the bottom being exposed to provide said conductingportion, a suspension arm being connected to the upper portion of saidsidewalls, the suspension arm including conducting material, saidconducting material being in electrical connection with the metal of theend walls, said means for making electrical connection to said exposedsurface including the metal of the end walls and the conducting materialof the suspension arm.

5. A rack according to claim 4, the conducting material of thesuspension arm being metal, the lower portion of the suspension armbeing covered with insulating material, and the upper portion of thesuspension arm being exposed to provide the conducting material of thesuspension arm for electrical connection thereto.

6. The method of electroplating the internal surface of an annular bodywhich comprises disposing said body coaxially with respect to alignedequal diameter openings in non-conducting side plates positioned one ateach end of the body in close fitting engaging relation therewith,

said body and side plates being immersed in an electrolysis bathoutfitted with an anode disposed externally of the annular body andcathode connection, electrically conmeeting the outer axially extendingsurface of the body to the cathode connection, and passing a currentthrough the bath to electroplate said internal surface.

References Cited UNITED STATES PATENTS 258,214 5/1882 Brinckmann 204-2971,010,638 12/1911 Kitchen 204-297 1,517,631 12/1924 Jones 204-287 HOWARDS. WILLIAMS, Primary Examiner. JOHN H. MACK, Examiner. D. R. JORDAN,Assistant Examiner.

